Start at the iliac crest (the top of your hipbone that you can feel like a shelf on the side of your body). From this level on your spine, measure to the C7 vertebrae, the knobby bone at the base of your neck when you put your head down. Make sure to keep your back straight while having the measurement taken.

Great for Snowshoes, too

I've done a few winter 14ers with the Kode and it works very well. No problems carrying snowshoes with the rear, center strap system, and the sides can handle an ice ax and trekking poles. My friends had frozen bladder hoses within a few hours, but I never had a problem with my CamelBak. In colder conditions, I'd add a chemical handwarmer to the bladder and bite valve pockets if needed.